Switch and circuit structure for electric heaters



April 13, 1954 l oc ou H I 2,675,447

SWITCH AND CIRCUIT STRUCTURE FOR ELECTRIC HEATERS Filed Oct. 5, 1950 FIG. 3.

T. /%y/ M ad/001k 4 FIG. 4. w M.

Patented Apr. 13, 1954 SWITCH AND CIR CUIT STRUCTURE FOR ELECTRIC HEATERS Paul J. McCullough, St. Louis, Mo., assignor, by

mesne assignments, to The Toastswell Company, Inc., .StwLnuis, Mo., a corporation of Missouri Application October 5, 1950,S.'erial No. 188,500

(CL' ZOO- 166) 4 Claims. 1

The invention relates. to electric circuit and switch structure particularly adapted. .for frequent on and off operation as required in domestic appliances such as electric toasters.

One object of the inventionv is to :produce a switch adapted for a device in which theswitch is operated under conditions where dust and other foreign matter, such as bread crumbs; are likely to interfere with the effioiency of the switch. A more particular object isto produce an economical, efiective, durable switch contact element.

The structure is generally used in devices in which the circuit is opened by clockwork and it is essential for the switch to offer unsubstantial resistance to its opening and it is a further object of the invention to attain this result without affecting the firm engagement of the contact surfaces when the switch is closed.

Another object of the invention is to simplify the connections of the heating elements to the current supply source to facilitate assembly and repair or replacement of the elements.

These objects are attained by the structure illustrated in the accompanying drawings in which:

Figure 1 is an elevation of the end of an electric toaster showing the switch and associated structure.

Figure 2 is a top view of the parts shown in Figure 1.

Figure 3 is a vertical detail section through the center of the switch contact button and its mounting and is drawn to an enlarged scale.

Figure 4 is a corresponding detail section showing the parts of the contact as they are being assembled.

Figure 5 is a. wiring diagram of the switch, current supply wire and heater elements.

The parts comprising the present invention are mounted upon a toaster housing end wall W, similarly to that shown in Patent No. 2,503,959 issued to the present inventor April 11, 1950. The heating elements A, B, C are in parallel and their circuits are controlled by the switch which includes the novel contact engaging member, best shown in Figure 3, which comprises a core I, of porcelain or other insulating material, and a bi-metal disc 2. The core has a head 3 and a neck or shank 4 and there may be a shallow groove 5 at the end of the shank nearest the head. Metal disc 2 preferably includes a relatively thick section 1 of brass, bronze, copper, steel or other relatively inexpensive metal, for rigidity, and is plated or otherwise has applied thereto'a're'latively thin layer 6 of silverfor high conductivity;

The disc' is formed originally with a-central opening N freely receiving the core shank l and when the core and disc are assembled they are placed on an anvil L, (Fig. 4) preferably with the disc slightly bowed. Upon descent of a hammer R; the disc'is'fiatten'ed so that the=inner periphery of its opening is reduced in "diameter and gripstheshankandenters the 'groove5', if the groove is present. Inaddition, or asan alternative. thehammer may compress the 'disc metal sufiiciently to extrude a portion of the metal inwardly of the disc opening to reduce the diameter of the opening.

Heating elements A, B and C are connected, in parallel to the bus bars D and E as best indicated in Figure 5. These bars are insulated from each other, except as they are connected by the heating elements, being mounted on insulation strips l3 and secured by four bolts l5 which also secure all the heater terminals IS. The supply wires are shown at I! and I8 and the circuit is completed when disc 2 engages contacts 8 and 9.

Core I of the contact engaging member is loosely mounted upon a stem 10 on the end of a crank arm ll, extending from a shaft I2, journaled on the toaster wall W. A sleeve l4, loosely surrounding stem it, serves as a spacer between core I and arm II, the lower end of the stem being enlarged to retain the disc.

Whenever the contact engaging member is moved from the on position, shown in full lines in Figure 1, to the ofi position, shown in broken lines in Figure l, the member will be free to rotate on shank l0 and normally will rotate so that a different area of the disc silver component 6 engages contacts 8 and 9, thus providing a multitude of engaging areas. The core and sleeve fit so loosely upon stem 50 that the core and disc may slide and tilt freely on the stem so that diametrically opposite surfaces of the disc will engage the contacts simultaneously.

Elements I! and :2 are of spring wire and are connected to the clockwork'(not shown) or other operating means for the toaster so as to effect the movement between the solid line and broken line positions shown in Figure 1 as the toasting operation is started. Elements H and i2 are so shaped that when the switch is closed there will be yielding pressure applied through the disc insuring firm engagement with the contacts and reducing the likelihood of arcing.

Even though the toaster cord is plugged into the house wiring, there will be no current passing through any of the toaster structure until the switch is closed. When contacts 8 and 9 are connected by disc 2, each heating element will receive the full voltage. Assembly, and disassembly for repair of the heaters and bus bars D, E, is readily effected by removing the nuts of bolts I 5.

The details of the construction may be varied substantially without departing from the spirit of the invention and the exclusive use of those modifications coming within the scope of the claims is contemplated.

What is claimed is:

1. An electric switch contact connector comprising a preformed rigid core of insulating material including a shank with a circumferential recess spaced from the ends of said core, and a metallic disc having an opening complementary to the recessed portion of said shank for reception of the disc therein, the diameter of the opening of said disc being less than the diameterof the unrecessed portion of the shank.

2. An electric switch contact connector comprising a preformed, rigid, relatively elongated dielectric body of circular cross section having a head portion, a shank portion of reduced diameter and an intervening shoulder, said shank being provided with a peripheral groove, and an electrically conductive annular disc tightly received within said groove and extending radially outward beyond said body.

3. An electric switch contact connector comprising a preformed, rigid, relatively elongated dielectric body of circular cross section having a head portion, a shank portion of reduced diameter and an intervening shoulder, said shank being provided with a, peripheral recess, one wall of which is continuous with said shoulder, and a fiat, annular conductive bimetallic disc received within said recess for snug frictional engagement of the adjacent shank and shoulder portions of the body, said disc having a diameter greater than that of the head portion whereby said disc extends radially outwardly therebeyond.

4. An electric switch contact connector as described in claim 3 wherein the metals forming the disc are stratified with one layer being rela tively thin and of higher conductivity than the other.

References Cited in the file of this patent UNITED STATES PATENTS 

